Multi-speed gearbox

ABSTRACT

Nine-speed multi-stage transmission with four planetary gear sets, rotatable shafts and six shift elements. Sun of first set is connected to fifth shaft which is couplable, via third brake, to housing and is connectable, via first clutch, to drive shaft which is connectable, via second clutch, to seventh shaft which is connected to ring of third set and carrier of second set. Drive shaft is connectable to eighth shaft, via third clutch, connected to carrier of first set and sun of second set. Sixth shaft is connected to ring of second set and carrier of fourth set. Fourth shaft is connected to ring of first set and sun of fourth set and is couplable, via second brake, to housing. Third shaft is connected to sun of third set and is couplable, via first brake, to housing. Output shaft is connected to carrier of third set and ring of fourth set.

This application is a National Stage completion of PCT/EP2013/055068filed Mar. 13, 2013, which claims priority from German patentapplication serial no. 10 2012 206 778.7 filed Apr. 25, 2012.

FIELD OF THE INVENTION

The present invention relates to a multi-stage transmission of aplanetary design, in particular an automatic transmission for a motorvehicle.

BACKGROUND OF THE INVENTION

According to the prior art, automatic transmissions, particularly formotor vehicles, comprise planetary gear sets that are shifted usingfriction elements or shift elements such as clutches and brakes, and aretypically connected to a start-up element, such as a hydrodynamic torqueconverter or a fluid coupling that is subject to a slip effect and isprovided optionally with a lock-up clutch.

Such an automatic transmission is known, for example, from DE 199 12 480B4 by the applicant. It comprises three single-carrier planetary gearsets, as well as three brakes and two clutches for shifting six forwardgears and one reverse gear, an input shaft and an output shaft, whereinthe carrier for the first planetary gear set is permanently connected tothe ring gear of the second planetary gear set, and the carrier for thesecond planetary gear set is permanently connected to the ring gear ofthe third planetary gear set, and the input shaft is directly connectedto the sun gear of the second planetary gear set.

Furthermore, in the known transmission, the input shaft can be connectedby means of the first clutch to the sun gear of the first planetary gearset, and by means of the second clutch to the carrier of the firstplanetary set, wherein the sun gear of the first planetary gear set canbe connected, by means of the first brake, to a housing of thetransmission, and the carrier of the first planetary gear set can beconnected, by means of the second brake, to the housing of thetransmission, wherein the sun gear of the third planetary gear set canbe connected, by means of the third brake, to the housing of thetransmission. The input shaft of the transmission is permanentlyconnected to the carrier for the third planetary gear set and the ringgear of the first planetary gear set.

Furthermore, a nine-speed multi-stage transmission is known from DE 2936 969 A1; it comprises eight shift elements and four planetary gearsets, wherein one planetary gear set serves as a front-mountedtransmission and the main gearing includes a Simpson set and a furtherplanetary gear set serving as reverse gearing.

Further multi-stage transmissions are known, for example, from theapplicant's DE 10 2005 010 210 A1 and DE 10 2006 006 637 A1.

Automatically shiftable vehicle transmissions of a planetary design arealready generally described numerous times in the prior art and arecontinually undergoing further development and improvement. Thesetransmissions should have a relatively simple design, in particularrequiring a small number of shift elements, and avoid the need fordouble shifting, i.e., engaging and/or disengaging two shift elements,when sequential shifting is performed, thereby ensuring that only oneshift element is ever switched when shifting is performed in definedgroups of gears.

The applicant's document, DE 10 2008 000 428 A1 discloses a multi-stagetransmission of a planetary design that includes an input drive and anoutput drive which are disposed in a housing. In the knowntransmissions, at least four planetary gear sets, referred to in thefollowing as the first, second, third and fourth planetary gear set, atleast eight rotatable shafts, referred to in the following as the driveshaft, output shaft, third, fourth, fifth, sixth, seventh and eighthshaft, as well as at least six shift elements, comprising brakes andclutches, are provided, the selective engagement of which producesdifferent transmission ratios between the input drive and the outputdrive so that preferably nine forward gears and one reverse gear can beimplemented.

The first and second planetary gear sets, which are preferably designedas minus planetary gear sets, thus having a negative stationarytransmission ratio, form a shiftable front-mounted gear set, wherein thethird and fourth planetary gear sets form a main gear set.

In the known multi-stage transmission, the carriers of the first and thesecond planetary gear sets are coupled together via the fourth shaft,which is connected to an element of the main gear set, the ring gear ofthe first planetary gear set is coupled to the sun gear of the secondplanetary gear set via the eighth shaft, which can be detachablyconnected to the drive shaft via the first clutch, and the sun gear ofthe first planetary gear set can be coupled to a housing of thetransmission by means of the third shaft, via a first brake, and can bedetachably connected to the drive shaft via a second clutch, wherein thering gear of the second planetary gear set can be coupled to a housingof the transmission by means of the fifth shaft, via a second brake. Inaddition, the seventh shaft is permanently connected to at least oneelement of the main gear set, and can be coupled to the housing of thetransmission via a third brake, and the sixth shaft is permanentlyconnected to at least one further element of the main gear set and canbe detachably connected to the drive shaft, via a third clutch; theoutput shaft is permanently connected at least to one further element ofthe main gear set.

In the known transmission, the fourth shaft is preferably permanentlyconnected to the ring gear of the third planetary gear set, the sixthshaft is permanently connected to the ring gear of the fourth planetarygear set and to the carrier of the third planetary gear set, and can bedetachably connected to the drive shaft via the third clutch.Furthermore, the seventh shaft is permanently connected to the sun gearsof the third and the fourth planetary gear sets, and can be coupled to ahousing of the transmission via the third brake. In this case, theoutput drive is produced via the output shaft that is permanentlyconnected to the carrier of the fourth planetary gear set. Furthermore,the third and the fourth planetary gear sets can be combined or reducedto a Ravigneaux set having a common carrier and a common ring gear.

According to the prior art, the shift elements of a multi-stagetransmission thus designed, which are usually designed as lamellarclutches or brakes, are actuated hydraulically, which disadvantageouslyresults in significant hydraulic losses. In order to avoid theseactuation losses, the use of shift elements that can be actuated upondemand would be especially advantageous.

Shift elements that can be actuated upon demand are understood, inparticular, to be those shift elements, in which maintaining the shiftstate requires no energy or little energy as compared to changing ashift state, thus, for example, from a disengaged shift state to anengaged shift state.

In order to make it possible to use shift elements that can be actuatedupon demand, the shift elements, in particular the clutches, should beeasily accessible from outside.

SUMMARY OF THE INVENTION

The object of the present invention is to propose a multi-stagetransmission of the type initially described, which has nine forwardgears and one reverse gear having a sufficient transmission ratio, inwhich the design complexity, the component load and the installationsize are optimized, and in which efficiency is improved. In addition,the shift elements of the transmission should be easily accessible fromoutside, which makes it possible to install shift elements that can beactuated upon demand. In addition, the transmission should be suitablefor standard design and for a frontal transverse design.

Accordingly, according to the invention, a multi-stage transmission of aplanetary design is proposed which has an input shaft and an outputshaft that are disposed in a housing. In addition, at least fourplanetary gear sets are provided. These are designated, in thefollowing, as the first, second, third, and fourth planetary gear sets,eight rotatable shafts which are designated, in the following, as thedrive shaft, output shaft, third, fourth, fifth, sixth, seventh, andeighth shafts, and six shift elements, preferably designed as lamellarshift elements or as a form locking shift element, comprising brakes andclutches, whose selective engagement produces different transmissionratios between the drive shaft and the output shaft, and thereforepreferably nine forward gears and one reverse gear can be implemented.

The first planetary gear set of the transmission is preferably designedas a plus planetary set, wherein the second, third and fourth aredesigned as minus planetary sets.

As is well known, a simple minus planetary gear set comprises a sungear, a ring gear, and a carrier on which the planetary gears arerotatably carried, the planetary gears meshing with the sun gear and thering gear. As a result, when the carrier is fixed, the ring gear has adirection of rotation that is opposite that of the sun gear. Incontrast, a simple plus planetary gear set comprises a sun gear, a ringgear and a carrier, on which inner and outer planet gears are rotatablycarried, wherein all inner planet gears mesh with the sun gear and allouter planet gears mesh with the ring gear, and each inner planet gearmeshes with only one outer planet gear. As a result, when the carrier isfixed, the ring gear has the same direction of rotation as the sun gear,and a positive stationary transmission ratio results.

According to a preferred embodiment of the invention, the sun gear ofthe first planetary gear set is connected to the fifth shaft which canbe coupled, via a third brake, to the housing of the transmission anddetachably connected, via a first clutch, to the drive shaft, whereinthe drive shaft can be detachably connected to the seventh shaft, via asecond clutch, which is connected to the ring gear of the thirdplanetary gear set and the carrier of the second planetary gear set, andwhich drive shaft can be detachably connected, via a third clutch, tothe eighth shaft which is connected to the carrier of the firstplanetary gear set and the sun gear of the second planetary gear set.

In addition, the sixth shaft is connected to the ring gear of the secondplanetary gear set and to the carrier of the fourth planetary gear set,wherein the fourth shaft is connected to the ring gear of the firstplanetary gear set and the sun gear of the fourth planetary gear set andcan be coupled, via a second brake, to the housing.

In addition, the third shaft of the transmission is connected to the sungear of the third planetary gear set and can be coupled, via a firstbrake, to the housing, wherein the output shaft is connected to thecarrier of the third planetary gear set and the ring gear of the fourthplanetary gear set.

Because the first, second and third clutch are disposed on the driveshaft of the transmission and the remaining shift elements are designedas brakes, good accessibility of all the shift elements of thetransmission is ensured, as a result of which the shift elements may bedesigned as shift elements that can be actuated upon demand. Within thecontext of further embodiments, shift elements of the transmission maybe designed, inter alia, as shift elements that can be hydraulicallyactuated.

In addition, transmission ratios that are especially suitable forpassenger vehicles are attained as well as a greater overall gear ratioof the multi-stage transmission, which results in improved drivingcomfort and a significant reduction in fuel consumption.

Furthermore, design complexity is significantly reduced with themulti-stage transmission, according to the invention, due to a smallnumber of shift elements. Using the multi-stage transmission accordingto the invention, it is advantageously possible to perform a start-upusing a hydrodynamic converter, an external start-up clutch, or anyother suitable external start-up element. It is also conceivable toperform a start-up using a start-up element integrated in thetransmission. Preferably, a shift element that is actuated in the firstforward gear and in the reverse gear is suitable for this.

Moreover, the multi-stage transmission, according to the invention,results in good efficiency in the main drive gears with respect to draglosses and gearing losses.

Low torques are advantageously present in the shift elements and in theplanetary gear sets of the multi-stage transmission, therebyadvantageously reducing wear in the multi-stage transmission. Inaddition, the low torques make it possible to utilize correspondinglylow dimensions, thereby reducing the necessary installation space andrelated costs. Furthermore, the rotational speeds of the shafts, shiftelements, and planetary gear sets are low.

In addition, the transmission, according to the invention, is designedto allow adaptability to different drive train embodiments in terms ofpower flow direction and spatial aspects.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in greater detail in the following, as anexample, with reference to the attached Figures. They show:

FIG. 1: a schematic view of a preferred embodiment of a multi-stagetransmission according to the invention; and

FIG. 2: an example of a shift pattern for a multi-stage transmissionaccording to FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a multi-stage transmission, according to the invention,which has a drive shaft 1, an output shaft 2, and four planetary gearsets P1, P2, P3, and P4 which are disposed in a housing G. In theexample shown in FIG. 1, the second, third, and fourth planetary gearsets P2, P3, P4 are designed as minus planetary gear sets, wherein thefirst planetary gear set P1 is designed as a plus planetary gear set.According to the invention, at least one of the additional planetarygear sets P1, P2, P3, P4 can be implemented as a plus planetary gear setif the carrier and ring gear connection are exchanged and,simultaneously, the value of the stationary transmission ratio isincreased by 1 in comparison to the embodiment as a minus planetary gearset.

In the embodiment shown here, viewed axially, the planetary gear setsP1, P2, P3, P4 are disposed in the sequence of the first planetary gearset P1, the second planetary gear set P2, the third planetary gear setP3, the fourth planetary gear set P4. According to the invention, theaxial sequence of the individual planetary gear sets and theconfiguration of the shift elements may be freely selected as long asthis allows the elements to connect.

As shown in FIG. 1, six shift elements are provided, namely, threebrakes, 03, 04, 05, and three clutches 15, 17, 18. The spatialdisposition of the shift elements can be arbitrary, and is limited onlyby the dimensions of the outer design. The clutches and the brakes ofthe transmission are preferably designed as friction elements orlamellar shift elements respectively, however they may also be designedas form-locking shift elements.

Selective shifting of nine forward gears and one reverse gear can beimplemented using these shift elements. The multi-stage transmission,according to the invention, has a total of eight rotatable shafts,namely, the shafts 1, 2, 3, 4, 5, 6, 7, and 8, wherein the drive shaftforms the first shaft and the output shaft forms the second shaft of thetransmission.

According to the invention, in the multi-stage transmission according toFIG. 1 it is provided that the sun gear of the first planetary gear setP1 is connected to the fifth shaft 5, which can be coupled, via a thirdbrake 05, to the housing G of the transmission and is detachablyconnected, via a first clutch 15, to the drive shaft 1, wherein thedrive shaft 1 can be detachably connected, via a second clutch 17, tothe seventh shaft 7, which is connected to the ring gear of the thirdplanetary gear set P3 and the carrier of the second planetary gear setP2, which drive shaft can be detachably connected, via a third clutch18, to the eighth shaft 8 which is connected to the carrier of the firstplanetary gear set P1 and the sun gear of the second planetary gear setP2.

As is evident from FIG. 1, the sixth shaft 6 is connected to the ringgear of the second planetary gear set P2 and to the carrier of thefourth planetary gear set P4, and the fourth shaft 4 is connected to thering gear of the first planetary gear set P1 and the sun gear of thefourth planetary gear set P4, and can be coupled, via a second brake 04,to the housing G.

Furthermore, the third shaft 3 is connected to the sun gear of the thirdplanetary gear set P3 and can be coupled, via a first brake 03, to thehousing G, wherein the output shaft 2 of the transmission is connectedto the carrier of the third planetary gear set P3 and the ring gear ofthe fourth planetary gear set P4.

In connection herewith, viewed axially, the first, second and thirdclutches 15, 17, 18 may be disposed side by side and may be designed aslamellar shift elements and have a common external disk carrier. In theembodiment shown, the first brake 03 in particular is suited for designas a dog clutch element, which significantly improves fuel consumption.

FIG. 2 shows an example of a shift pattern of a multi-stage transmissionaccording to FIG. 1. Three shift elements are engaged for every gear.The shift pattern shows, as examples, the particular transmission ratiosi of the individual gear steps and, to be determined therefrom, the gearincrements or step changes φ to the next higher gear, wherein the value9.012 is the transmission ratio spread.

In the example shown, the values for the stationary transmission ratiosof the planetary gear sets P1, P2, P3, P4, implemented as minusplanetary gear sets, are 1.946, −3.676, −2.767, and −2.062,respectively. FIG. 2 shows that only one shift element must be engagedand one shift element must be disengaged when shifting sequentially,since two neighboring gear steps jointly use two shift elements. It isalso shown that a large transmission ratio spread is attained with smallgear increments.

The first forward gear is attained by engaging the first and secondbrakes 03, 04 and the third clutch 18, the second forward gear isattained by engaging the first and third brakes 03, 05 and the thirdclutch 18, the third forward gear is attained by engaging the firstbrake 03 and the first and third clutches 15, 18, the fourth forwardgear is attained by engaging the first brake 03 and the first and secondclutches 15, 17, the fifth forward gear, which is designed as a directgear in the example shown, is attained by engaging the first, second,and third clutches 15, 17, 18, the sixth forward gear is attained byengaging the third brake 05 and the second and third 17, 18, the seventhforward gear is attained by engaging the second brake 04 and the secondand third clutches 17, 18, the eighth forward gear is attained byengaging the second and third brakes 04, 05 and the second clutch 17,and the ninth forward gear is attained by engaging the second brake 04and the first and second clutches 15, 17, wherein the reverse gear isattained by engaging the first and second brakes 03, 04 and the firstclutch 15.

Alternatively, the fourth forward gear may be shifted by means ofadditional shift combinations, which are designated as M in FIG. 2.Accordingly, the fourth forward gear can be attained by engaging thefirst and second brakes 03, 04 and the second clutch 17, or by engagingthe first brake 03 and the second and third clutches 17, 18, or byengaging the first and third brakes 03, 05 and the second clutch 17.

Since the first and second brakes 03, 04 and the first and thirdclutches 15, 18 are engaged in the first forward gear and/or in thereverse gear, these shift elements can be used as start-up elements.

According to the invention, different gear increments also result fromthe same shift pattern depending on the shift logic, thereby making itpossible to implement an application-specific or vehicle-specificvariation.

According to the invention, it is also optionally possible to provideadditional freewheels at each suitable location of the multi-stagedtransmission, for example, between a shaft and the housing, or possiblyto connect two shafts.

An axle differential and/or a distributor differential can be disposedon the drive side or on the output side.

Within the scope of an advantageous development of the invention, thedrive shaft 1 can be separated from a drive motor, as needed, by aclutch element, wherein a hydrodynamic converter, a hydraulic clutch, adry start-up clutch, a wet start-up clutch, a magnetic powder clutch, ora centrifugal clutch or the like can be used as the clutch element. Itis also possible to dispose such a start-up element in the power flowdirection after the transmission wherein, in this case, the drive shaft1 is permanently connected to the crankshaft of the drive motor.

The multi-stage transmission, according to the invention, also makes itpossible to situate a torsional-vibration damper between the drive motorand the transmission.

Within the scope of a further, not depicted embodiment of the invention,a wear-free brake, for instance, a hydraulic or electric retarder or thelike, can be disposed on each shaft, preferably on the drive shaft 1 orthe output shaft 2 which, in particular, is of special significance foruse in commercial vehicles. Furthermore, a power take-off drive can beprovided on each shaft, preferably on the input shaft 1 or the outputshaft 2, for driving additional assemblies.

The friction shift elements that are used can be designed as powershiftable clutches or brakes. In particular, force locking clutches orbrakes can be used, for instance, lamellar clutches, band brakes, and/orcone clutches.

A further advantage of the multi-stage transmission presented here isthat an electric machine can be attached to each shaft as a generatorand/or as an additional drive machine.

REFERENCE CHARACTERS

-   1 first shaft, drive shaft-   2 second shaft, output shaft-   3 third shaft-   4 fourth shaft-   5 fifth shaft-   6 sixth shaft-   7 seventh shaft-   8 eighth shaft-   03 first brake-   04 second brake-   05 third brake-   15 first clutch-   17 second clutch-   18 third clutch-   G housing-   P1 first planetary gear set-   P2 second planetary gear set-   P3 third planetary gear set-   P4 fourth planetary gear set-   i transmission ratio-   φ step change

The invention claimed is:
 1. A multi-stage transmission of a planetarydesign comprising: a drive shaft (1), an output shaft (2), first,second, third and fourth planetary gear sets (P1, P2, P3, P4) disposedwithin a housing each of the first, second, third, and fourth planetarygear sets including a sun gear, a ring gear, and a carrier (G), third,fourth, fifth, sixth, seventh and eighth rotatable shafts (3, 4, 5, 6,7, 8), six shift elements (03, 04, 05, 14, 17, 18), comprising brakes(03, 04, 05) and clutches (14, 17, 18), whose selective engagementproducing different transmission ratios between the drive shaft (1) andthe output shaft (2) so that nine forward gears and one reverse gear areimplementable, wherein the sun gear of the first planetary gear set (P1)is connected to the fifth shaft (5), the fifth shaft (5) can be coupled,via a third brake (05), to the housing (G), the fifth shaft (5) can bedetachably connected, via a first clutch (15), to the drive shaft (1),the drive shaft (1) can be detachably connected, via a second clutch(17), to the seventh shaft (7), the seventh shaft which is connected toboth the ring gear of the third planetary gear set (P3) and the carrierof the second planetary gear set (P2), the drive shaft (1) can bedetachably connected, via a third clutch (18), to the eighth shaft (8),the eighth shaft (8) is connected to both the carrier of the firstplanetary gear set (P1) and the sun gear of the second planetary gearset (P2), the sixth shaft (6) is connected to both the ring gear of thesecond planetary gear set (P2) and the carrier of the fourth planetarygear set (P4), the fourth shaft (4) is connected to both the ring gearof the first planetary gear set (P1) and the sun gear of the fourthplanetary gear set (P4), and the fourth shaft (4) can be coupled, via asecond brake (04), to the housing (G), the third shaft (3) is connectedto the sun gear of the third planetary gear set (P3) and can be coupled,via a first brake (03), to the housing (G), and the output shaft (2) isconnected to both the carrier of the third planetary gear set (P3) andthe ring gear of the fourth planetary gear set (P4).
 2. The multi-stagetransmission according to claim 1, wherein the first planetary gear set(P1) is designed as a plus planetary gear set, and the second, the thirdand the fourth planetary gear sets (P2, P3, P4) are designed as minusplanetary gear sets.
 3. The multi-stage transmission according to claim1, wherein, when viewed axially, the first, the second, the third andthe fourth planetary gear sets (P1, P2, P3, P4) are disposed in thesequence of the first planetary gear set (P1), the second planetary gearset (P2), the third planetary gear set (P3), and the fourth planetarygear set (P4).
 4. The multi-stage transmission according to claim 1,wherein the six shift elements (03, 04, 05, 15, 17, 18) of thetransmission are designed as shift elements that can be actuated upondemand.
 5. The multi-stage transmission according to claim 1, whereinthe first brake (03) is designed as a form-locking shift elements. 6.The multi-stage transmission according to claim 1, wherein a firstforward gear is attained by engaging the first and the second brakes(03, 04) and the third clutch (18), a second forward gear is attained byengaging the first and the third brakes (03, 05) and the third clutch(18), a third forward gear is attained by engaging the first brake (03)and the first and the third clutches (15, 18), a fourth forward gear isattained by engaging the first brake (03) and the first and the secondclutches (15, 17), a fifth forward gear is attained by engaging thefirst, the second and the third clutches (15, 17, 18), a sixth forwardgear is attained by engaging the third brake (05) and the second and thethird clutches (17, 18), a seventh forward gear is attained by engagingthe second brake (04) and the second and the third clutches (17, 18), aneighth forward gear is attained by engaging the second and the thirdbrakes (04, 05) and the second clutch (17), a ninth forward gear isattained by engaging the second brake (04) and the first and the secondclutches (15, 17), and the reverse gear is attained by engaging thefirst and the second brakes (03, 04) and the first clutch (15).
 7. Themulti-stage transmission according to claim 1, wherein a first forwardgear is attained by engaging the first and the second brakes (03, 04)and the third clutch (18), a second forward gear is attained by engagingthe first and the third brakes (03, 05) and the third clutch (18), athird forward gear is attained by engaging the first brake (03) and thefirst and the third clutches (15, 18), a fourth forward gear is attainedby engaging the first and the second brake (03, 04) and the secondclutch (17), a fifth forward gear is attained by engaging the first, thesecond and the third clutches (15, 17, 18), a sixth forward gear isattained by engaging the third brake (05) and the second and the thirdclutches (17, 18), a seventh forward gear is attained by engaging thesecond brake (04) and the second and the third clutches (17, 18), aneighth forward gear is attained by engaging the second and the thirdbrakes (04, 05) and the second clutch (17), a ninth forward gear isattained by engaging the second brake (04) and the first and the secondclutches (15, 17), and the reverse gear is attained by engaging thefirst and the second brakes (03, 04) and the first clutch (15).
 8. Themulti-stage transmission according to claim 1, wherein a first forwardgear is attained by engaging the first and the second brakes (03, 04)and the third clutch (18), a second forward gear is attained by engagingthe first and the third brakes (03, 05) and the third clutch (18), athird forward gear is attained by engaging the first brake (03) and thefirst and the third clutches (15, 18), a fourth forward gear is attainedby engaging the first brake (03) and the second and the third clutches(17, 18), a fifth forward gear is attained by engaging the first, thesecond and the third clutches (15, 17, 18), a sixth forward gear isattained by engaging the third brake (05) and the second and the thirdclutches (17, 18), a seventh forward gear is attained by engaging thesecond brake (04) and the second and the third clutches (17, 18), aneighth forward gear is attained by engaging the second and the thirdbrakes (04, 05) and the second clutch (17), a ninth forward gear isattained by engaging the second brake (04) and the first and the secondclutches (15, 17), and the reverse gear is attained by engaging thefirst and the second brakes (03, 04) and the first clutch (15).
 9. Themulti-stage transmission according to claim 1, wherein a first forwardgear is attained by engaging the first and the second brakes (03, 04)and the third clutch (18), a second forward gear is attained by engagingthe first and the third brakes (03, 05) and the third clutch (18), athird forward gear is attained by engaging the first brake (03) and thefirst and the third clutches (15, 18), a fourth forward gear is attainedby engaging the first and the third brakes (03, 05) and the secondclutch (17), a fifth forward gear is attained by engaging the first, thesecond and the third clutches (15, 17, 18), a sixth forward gear isattained by engaging the third brake (05) and the second and the thirdclutches (17, 18), a seventh forward gear is attained by engaging thesecond brake (04) and the second and the third clutches (17, 18), aneighth forward gear is attained by engaging the second and the thirdbrakes (04, 05) and the second clutch (17), a ninth forward gear isattained by engaging the second brake (04) and the first and the secondclutches (15, 17), and the reverse gear is attained by engaging thefirst and the second brakes (03, 04) and the first clutch (15).
 10. Themulti-stage transmission according to claim 1, wherein the multi-stagetransmission is an automatic transmission for a motor vehicle.
 11. Amulti-stage transmission of a planetary design comprising: a driveshaft, an output shaft, first, second, third and fourth planetary gearsets disposed within a housing each of the first, second, third, andfourth planetary gear sets including a sun gear, a ring gear, and acarrier, third, fourth, fifth, sixth, seventh and eighth rotatableshafts, six shift elements, comprising brakes and clutches, whoseselective engagement producing different transmission ratios between thedrive shaft and the output shaft so that nine forward gears and onereverse gear are implementable, wherein the sun gear of the firstplanetary gear set is connected to the fifth shaft, the fifth shaft canbe coupled, via a third brake, to the housing, the fifth shaft can bedetachably connected, via a first clutch, to the drive shaft, the driveshaft can be detachably connected, via a second clutch, to the seventhshaft, the seventh shaft which is connected to both the ring gear of thethird planetary gear set and the carrier of the second planetary gearset, the drive shaft can be detachably connected, via a third clutch, tothe eighth shaft, the eighth shaft is connected to both the carrier ofthe first planetary gear set and the sun gear of the second planetarygear set, the sixth shaft is connected to both the ring gear of thesecond planetary gear set and the carrier of the fourth planetary gearset, the fourth shaft is connected to both the ring gear of the firstplanetary gear set and the sun gear of the fourth planetary gear set,and the fourth shaft can be coupled, via a second brake, to the housing,the third shaft is connected to the sun gear of the third planetary gearset and can be coupled, via a first brake, to the housing, and theoutput shaft is directly connected to both the carrier of the thirdplanetary gear set and the ring gear of the fourth planetary gear set.12. The multi-stage transmission according to claim 11, wherein a firstforward gear is attained by engaging the first and the second brakes andthe third clutch, a second forward gear is attained by engaging thefirst and the third brakes and the third clutch, a third forward gear isattained by engaging the first brake and the first and the thirdclutches, a fourth forward gear is attained by engaging the first brakeand the first and the second clutches, a fifth forward gear is attainedby engaging the first, the second and the third clutches, a sixthforward gear is attained by engaging the third brake and the second andthe third clutches, a seventh forward gear is attained by engaging thesecond brake and the second and the third clutches, an eighth forwardgear is attained by engaging the second and the third brakes and thesecond clutch, a ninth forward gear is attained by engaging the secondbrake and the first and the second clutches, and the reverse gear isattained by engaging the first and the second brakes and the firstclutch.
 13. The multi-stage transmission according to claim 11, whereina first forward gear is attained by engaging the first and the secondbrakes and the third clutch, a second forward gear is attained byengaging the first and the third brakes and the third clutch, a thirdforward gear is attained by engaging the first brake and the first andthe third clutches, a fourth forward gear is attained by engaging thefirst and the second brake and the second clutch, a fifth forward gearis attained by engaging the first, the second and the third clutches, asixth forward gear is attained by engaging the third brake and thesecond and the third clutches, a seventh forward gear s attained byengaging the second brake and the second and the third clutches, aneighth forward gear is attained by engaging the second and the thirdbrakes and the second clutch, a ninth forward gear is attained byengaging the second brake and the first and the second clutches, and thereverse gear is attained by engaging the first and the second brakes andthe first clutch.
 14. The multi-stage transmission according to claim11, wherein a first forward gear is attained by engaging the first andthe second brakes and the third clutch, a second forward gear isattained by engaging the first and the third brakes and the thirdclutch, a third forward gear is attained by engaging the first brake andthe first and the third clutches, a fourth forward gear is attained byengaging the first brake and the second and the third clutches, a fifthforward gear is attained by engaging the first, the second and the thirdclutches, a sixth forward gear is attained by engaging the third brakeand the second and the third clutches, a seventh forward gear isattained by engaging the second brake and the second and the thirdclutches, an eighth forward gear is attained by engaging the second andthe third brakes and the second clutch, a ninth forward gear is attainedby engaging the second brake and the first and the second clutches, andthe reverse gear is attained by engaging the first and the second brakesand the first clutch.
 15. The multi-stage transmission according toclaim 11, wherein a first forward gear is attained by engaging the firstand the second brakes and the third clutch, a second forward gear isattained by engaging the first and the third brakes and the thirdclutch, a third forward gear is attained by engaging the first brake andthe first and the third clutches, a fourth forward gear is attained byengaging the first and the third brakes and the second clutch, a fifthforward gear is attained by engaging the first, the second and the thirdclutches, a sixth forward gear is attained by engaging the third brakeand the second and the third clutches, a seventh forward gear isattained by engaging the second brake and the second and the thirdclutches, an eighth forward gear is attained by engaging the second andthe third brakes and the second clutch, a ninth forward gear is attainedby engaging the second brake and the first and the second clutches, andthe reverse gear is attained by engaging the first and the second brakesand the first clutch.
 16. The multi-stage transmission according toclaim 11, wherein the multi-stage transmission is an automatictransmission for a motor vehicle.